The present invention relates to a method and a device for monitoring an interval between a first injection operation and a second injection operation of a combustion cycle in a cylinder of an internal combustion engine in which the individual injection operations are controlled by an electrical actuator element.
In known methods and devices for controlling the fuel metering in an injection operation of a combustion cycle in a cylinder of an internal combustion engine, solenoid valves are used for controlling the beginning and the end of the injection.
In today""s internal combustion engines, the actual injection is divided into multiple partial injection operations. A pilot injection is preferably carried out in each combustion cycle of a cylinder, in which a small amount is injected, and a main injection operation, in which the main amount of fuel is injected. In a four-stroke internal combustion engine, the combustion cycle includes an intake stroke, a compression stroke, a working stroke, and an exhaust stroke. In addition to a pilot injection operation and a main injection operation, other partial injection operations can be provided. Thus, for example, a post-injection operation can be provided for cleaning the combustion chamber. Furthermore, the pilot injection operation, the main injection operation and/or the post-injection operation can be divided into a plurality of partial injection operations.
German Patent 198 60 393 proposes that the beginning of activation for a subsequent pilot injection for a cylinder be computed on the basis of a desired interval between the pilot injection and the main injection in this cylinder and the beginning of activation of the main injection for a previous injection in a previous cylinder. The interval between the pilot injection and the main injection is defined as a function of at least the rotational speed of the internal combustion engine and the injected amount of fuel.
U.S. Pat. No. 5,402,760 describes a fuel injection controller for an internal combustion engine having a controller which has an interrupting device in order to suppress fuel injection between a pilot injection and a main injection.
These types of multiple injections, the problem arises that the individual injection operations often overlap. This results, for example, in part of the amount of fuel intended for a pilot injection operation being injected into the cylinder during the main injection operation. This is known as injection overlap. Injection overlap and the associated uncontrolled increase in the amount of fuel for an injection operation has a negative effect on the exhaust gases of the engine, the engine torque, and the noise emission in cam-driven systems.
The object of the present invention is to provide a method and a device for monitoring an interval between a first injection operation and a second injection operation of a combustion cycle in a cylinder of an internal combustion engine in which the individual injection operations are controlled by an electrical actuator element.
This objective is achieved by the features presented in claims 1 and 9.
The present invention advantageously makes a well-defined separation of the individual injection operations possible, even in the case of an unforeseen event, such as a sudden drop in the battery voltage.
Advantageous and expedient implementations and refinements of the present invention are presented in the subclaims.